In most homes, the attic door or hatch, is a framed plywood square in the ceiling of a hallway or bedroom, with no insulation above it. Without insulation, it is like having an open door to the outside or an open fireplace flue.
The good news is, it's easy to fix this problem: simply apply a piece of insulated foam board to the back of the door or hatch and add weatherstripping to the frame. The materials are cheap, widely available and easy to work with, and the project takes half an hour to do. At a total cost of about $20, this project pays itself back in about 8 months -- and gives you ongoing energy savings for the life of your home.